1. Field of the Invention
The present invention relates to a method for producing optically active acyloin compounds, which are useful for intermediates of medicines and the like, a binaphthol monoether complex using for the method, and a method for producing the complex.
2. Description of the Prior Art
Optically active acyloin compounds can be used as raw materials of optically active oxodicyclopentadiene, which are useful as starting materials of physiologically active materials such as pharmaceuticals (Japanese Patent Application No. 9-213840). For example, it is known that such compounds are starting materials of Aphanophine having analgetic effect. (J. Chem. Soc. Chem. Commun., 290 (1990)).
However, the method for producing optically active acyloin compounds is not known except a method using optical resolution (Japanese Patent Application 9-213840).
Although monomethyl ether of binaphthol monoether-tin tetrachloride complex is used for asymmetric hydrogenation of prochiral silyl enol ether by Yamamoto et al., there is no example that the complex is utilized for the compound represented by formula (1).
Hitherto, a method for producing the binaphthol monoether has been inefficient, because the useless isomer of ether products should be decomposed and removed by obtaining a derivative of a diastereomer as described by Tada et al. (J. Chem. Soc., Perk in Trans. 2, 1997) or by Salbadori et al. (Tetrahedron, 1987, 43, 4969) or by using HPLC as described by Park et al. (J. Org. Chem., 1982, 47, 4037).
As described above, as a method for producing optically active acyloin compounds, a method using optical resolution is known. The optical resolution method is effective when both enantiomers are required, but the method is ineffective when either one of the enantiomers is needed.